The investigation, based on interviews with local Libyans and US officials, "turned up no evidence that Al Qaeda or other international terrorist groups had any role in the assault," according to the report.

"The attack was led, instead, by fighters who had benefited directly from NATO’s extensive air power and logistics support during the uprising against Colonel Qaddafi" - the Libyan dictator ousted in 2011.

While the report convincingly outlines the series of events that led to the death of US Ambassador Chris Stevens and three other Americans, some members of Congress - especially Republicans - have repeatedly insisted Benghazi was an Al Qaeda mission.

"It was very clear to the individuals on the ground that this was an Al Qaeda-led event. And they had pretty fairly descriptive events early on that lead those folks on the ground, doing the fighting, to the conclusion that this was a pre-planned, organized terrorist event," said Rep. Mike Rogers, R-Mich., in November.

And so the Benghazi attack became a heated debate in Washington, as varying narratives of that day found support along party lines, with Republican's claiming the Obama administration had attempted to cover up Al Qaeda's involvement for political reasons.

But the Times report states Libyan Ahmed Abu Khattala, "who had no known affiliations with terrorist groups," had the key role in organizing the assault. He is now the prime suspect in the criminal investigation into the killings. (Khattala denies his role in the attack).

The Times also seeks to put an end to the claim made by some members of Congress that an American-made video - the "Innocence of Muslims" - had no part in the attack, which closely followed its release. The video denigrated Islam and had helped instigate anger that fueled the attack.

In 2012, the US State Department commissioned an investigation into the attack that found security at the consulate had been deficient, though still, there had been "no immediate, specific" intelligence pointing to threats.

The only connection the Times found between the Benghazi attack and Al Qaeda was a phone call in which someone involved in the attack notified a friend in Africa who reportedly has ties to Al Qaeda.